The clustering of sub- millimetre galaxies: are they the - - PowerPoint PPT Presentation

The clustering of sub- millimetre galaxies: are they the progenitors of local massive ellipticals?

AARON WILKINSON, OMAR ALMAINI, CHIAN-CHOU CHEN, IAN SMAIL, VINODIRAN

ARUMUGAM, ANDREW BLAIN, EDWARD L. CHAPIN, SCOTT C. CHAPMAN, CHRISTOPHER J CONSELICE, WILLIAM COWLEY, JAMES S. DUNLOP, DUNCAN FARRAH, JAMES GEACH, WILLIAM G. HARTLEY, ROB IVISON, DAVID MALTBY, MICHAL J. MICHALOWSKI, ALICE MORTLOCK, DOUGLAS SCOTT, CHRIS SIMPSON, JAMES S. SIMPSON, PAUL VAN DER WERF, VIVIENNE WILD ppxakw@nottingham.ac.uk

SMG20 2017

Motivation

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Processes responsible for the assembly of local massive elliptical galaxies are not well understood.

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One way of studying the formation of these galaxies is to analyse the clustering evolution of the progenitor candidate, sub-millimetre galaxies (SMGs), which can be done for the first time.

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From the clustering analysis, we can determine the mass of the dark matter halo.

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Identify the true descendants of SMGs.

UKIDSS Ultra Deep Survey (PI: O. Almaini)

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Sample drawn from the K-band of the UDS survey

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Covers area of 0.88 square degrees

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DR8: K=24.6, H=24.2, J=24.9 (DR11: K=25.3)

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Deepest infrared survey covering such a large area

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Photometric redshifts derived from 11- band photometry

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δz/(1+z)~ 0.03 Hartley et al. 2013

SCUBA-2 Cosmology Legacy Survey

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Submillimetre Common-User Bolometer Array at the JCMT

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Observe 850um fluxes within ~15” beam, with sensitivity down to several mJy.

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Identify counterparts to poor resolution sources using radio maps and Optical Infrared Triple Colour criteria (OIRTC; trained on ALMA sample) C.-C. Chen et al. (2016), ApJ, 820, 82

Clustering Analysis

Angular 2-point correlation function

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Measures the excess number of galaxy pairs as a function of angular separation θ, with respect to a random distribution.

Angular 2-point correlation function

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Measures the excess number of galaxy pairs as a function of angular separation θ, with respect to a random distribution.

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DM power spectrum -> Fourier transform + project -> DM correlation function

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Multiplication factor is the galaxy bias squared, b2

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Derive halo masses from the galaxy bias (Mo & White 2002)

x b2

Passive & star-forming halo masses

Wilkinson et al. 2017 WEAK CLUSTERING STRONG CLUSTERING

SMG halo masses

STRONG CLUSTERING WEAK CLUSTERING Wilkinson et al. 2017

Correcting for blending bias…

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By using smaller redshift slices, blending bias is reduced… Wilkinson et al. 2017 Cowley et al. 2016, 2017b

Take SMG halo masses…

STRONG CLUSTERING WEAK CLUSTERING Wilkinson et al. 2017

… and grow them (Fakhouri+2010)

STRONG CLUSTERING WEAK CLUSTERING Wilkinson et al. 2017

SMGs – progenitors of massive ellipticals

STRONG CLUSTERING WEAK CLUSTERING Wilkinson et al. 2017

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2<z<2.5 SMGs -> local massive elliptical galaxies; with matching number densities

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z>2.5 SMGs -> BCGs

Post-starburst galaxies

u “k+a” galaxies: Recently quenched (<1Gyr)

after intense period of star formation

u Spectral features: Balmer breaks and strong

Hδ absorption lines.

u Identified photometrically using PCA

technique (see Wild+2014)

u Spectral confirmation: it works!! (Wild+2014,

Maltby+2016)

STRONG CLUSTERING WEAK CLUSTERING

SMGs go through a post-starburst phase?

STRONG CLUSTERING WEAK CLUSTERING Wilkinson et al. in prep

PRELIMINARY…

Conclusions

u SMG clustering signal indistinguishable from normal star-forming counterparts

=> SMGs = high-mass dusty subset of main-sequence galaxies.

u SMGs show a downsizing trend with halo mass, as the Universe ages. u Evolution sequence: u What more could be done to test the connection between SMGs and other

galaxy populations? How do SMGs shut off their star-formation?

SMG -> (Post-starburst) -> Present-day massive ellipticals

Comparison to previous studies

Identifying SMG counterparts

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Identify counterparts using radio maps and Optical Infrared Triple Colour criteria (OIRTC; trained on ALMA sample)

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Radio: identifies the brightest SMGs

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OIRTC: (z – K), ([3.6] – [4.5]) and (K – [3.6])

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A sample of ~600 SMG counterparts in total Chen et al. (2016)

Identifying PSB galaxies – the PCA

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The PCA - each SED is composed of a linear combination of 3 eigenvectors

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Amplitude of eigenvectors = Supercolours

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Calculate galaxy properties and classify galaxies Wild et al. 2014

Identifying PSB galaxies – the PCA

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The PCA - each SED is composed of a linear combination of 3 eigenvectors

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Amplitude of eigenvectors = Supercolours

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Calculate galaxy properties and classify galaxies Wild et al. 2014

Galaxy classification

u Data from the UKIDSS Ultra

Deep Survey DR8

u Identified ~1000 PSB galaxies

in the UKIDSS UDS at 0.5<z<2.0, the largest high-redshift sample to date

u Spectra confirmation is

• ngoing – so far we have

spectra for 30 PSB candidates

FRACTION OF MASS STELLAR AGE DUST CONTENT